Circuit board inter-connection system and method

ABSTRACT

An electrical inter-connection is provided such that a terminal pin which is positioned in a pin block extends through a plated through-hole in a circuit board substrate and is connected with the circuit board using a conductive bonding agent such as solder. The terminal pin is capable of inter-connection with conductive elements located on each major side of the circuit board and eliminates the need for an interference fit between the terminal pin and circuit board. The pin block includes a body and at least one stand-off. The stand-off maintains the body a sufficient distance from the circuit board substrate to enable a solder fillet to form between the plated through-hole and the terminal pin during re-flow processing. The electrical inter-connection further includes an eccentric aperture in the circuit board suitable for interference fit inter-connection with a protruding cylindrical feature such as on an electrical ground that has poor solderability characteristics. The preferred embodiment limits normal forces caused by temperature cycling, vibration, and other conditions to two areas of contact yet enables adequately low electrical contact resistance.

This application is a divisional of, and claims benefit of priorityfrom, U.S. nonprovisional patent application Ser. No. 10/666945, whichclaims benefit of priority from U.S. provisional patent application Ser.No. 60/412750, which was filed Sep. 23, 2002, and which is herebyincorporated by reference.

TECHNICAL FIELD

The present invention relates to systems and methods for providingelectrical connections, and more particularly, to systems and methodsfor providing electrical connections with one or more electricalterminals and a circuit board.

BACKGROUND OF THE INVENTION

There is a growing need for electrical connections where conductiveelements such as electrical connectors, circuit boards, and electronicmodules located on each major side of a circuit board must be connectedwith each other and with the circuit board. U.S. Pat. No. 6,413,119, toGabrisko, Jr. et al., which is incorporated herein for backgroundpurposes, discloses a filtered electrical connector, in which conductivepins (shown at 20) extend through a first circuit board (filter insertshown at 22) for connection with a mating connector on a first side anda second circuit board on a second side apposing the first side.

The above cited '119 patent discloses an electrical connection having afilter insert (shown at 22) comprising a plated thermoplastic substrate(generally shown at 48) which exhibits an-isotropic thermal expansionproperties and includes electrical devices (such as capacitors shown at64) connected with the filter insert. The major lengths of theseelectrical devices are oriented along a direction of reduced thermalexpansion properties of the substrate. It should be noted that aterminal may be press-fit into a plated through-hole in a circuit boardto produce this type of connection.

As packaging sizes and distances between centerlines continue todecrease, and as manufacturers seek to reduce costs, however, there isan increasing need for systems and methods for providing connections,whereby normal forces and stresses that are incurred during production(e.g., during insertion), which may cause damage or fatigue to, forexample, circuit traces, solder joints, and electronic components.Stresses, such as those that may be created among a terminal and acircuit board, may also impose constraints on the designs of suchdevices, particularly when the devices and their connections are to besubjected to harsh environments, such as those found in vehicles (e.g.,automobiles, aircraft, and the like), in heavy machinery or other highstress, shock-prone applications. Such design difficulties may alsoinhere in applications where size and/or weight is a significant factor(e.g., medical instruments). It should also be noted that cast contactpins in a connector housing may be force-fit into plated molded holes inthe filter insert to establish good electrical contact for grounding thefilter insert.

It should be noted that one advantage of such as a filtered insertsubstrate is that an-isotropic properties of the substrate material maybe utilized to decrease the undesirable impacts (e.g., thermalexpansion, stresses resulting from harsh environments) may impose oninterference-fit connections (e.g., among one or more conductive pinsand a circuit board, among one or more contact pins and a circuitboard). Additionally, detailed features, such as holes configured forconnection with electrical ground, may be molded into the material.

Despite these advantages, however, presently known approaches typicallyentail relatively high cost and complexity. For example, the requisiteplating processes, the necessary use of an-isotropic thermoplasticmaterials, and their associated materials and tooling all typicallycontribute to increased complexity and cost.

It would therefore be beneficial to have a system and method that wouldenable use of low cost circuit board substrates, such as an FR-4 epoxyglass laminate having circuit traces and plated through-holes andproduced through conventional plating processes, in applications wherebyconductive elements located on a first major side of a circuit board maybe inter-connected with the circuit board and with conductive elementslocated on a second major side of the circuit board. It would furtherbeneficial to have a system and method that would provide electricalgrounding of a circuit board, despite poor ground solderabilitycharacteristics, with reduced cost and increased reliability. It wouldfurther be desirable to have a system and method whereby such grounding,and any connections involved in such system and method, could beaccomplished with significantly reduced, or eliminated, insertionforces, whereby normal forces and stresses that damage circuit traces,solder joints, and electronic components, might be reduced oreliminated.

SUMMARY OF THE INVENTION

The methods and apparatus of the present invention address many of theshortcomings of the prior art. In accordance with various aspects of thepresent invention, methods and systems provide improved electricalinter-connection among a circuit board and one or more conductiveelements located on each major side of the circuit board, accommodatinguse of low-cost circuit board substrates while providing electricalgrounding and significantly reducing or eliminating insertion forces andstresses that might otherwise damage circuit traces, solder joints, andelectronic components.

In an exemplary embodiment of the present invention, an electricalinter-connection system comprises a circuit board substrate, aconductive pad, a conductive terminal, and a conductive bonding agentsuch as solder. The circuit board substrate has first and secondsurfaces and includes a through-hole extending between them. Theconductive pad is disposed on the first surface, being positionedsubstantially adjacent the through-hole. The conductive terminal hasfirst and second ends and extends through the through-hole such that itsends are exposed for electrical inter-connection with one or more matingelements, e.g., extending at least about 2 mm beyond the respectivefirst and second surfaces of the circuit board substrate. Finally, theconductive bonding agent electrically connects the conductive terminalwith the conductive pad.

In one exemplary embodiment, an electrical inter-connection systemincludes conductive plating in the through-hole and electricallyconnected with the conductive bonding agent. In another exemplaryembodiment, a system includes a second conductive pad disposed on thesecond surface of the substrate, substantially adjacent thethrough-hole. In this embodiment, the conductive bonding agent alsoelectrically connects the terminal with the second conductive pad.

In an exemplary embodiment, an electrical inter-connection system alsoincludes a dielectric housing having a body and at least one stand-off.In accordance with this embodiment, the terminal is positioned in thehousing, the stand-offs are mounted on the first surface, and the bodyis located a sufficient distance from the circuit board to enable asolder fillet to form between the conductive terminal and the conductivepad. The body may also have a board mounting face and an opposed matingface; the at least one stand-off may extend from the board mountingface; a first end of the terminal may extend outwardly from the boardmounting face; a second end of the terminal may extend outwardly fromthe mating face; and the stand-off may engage the first surface of thesubstrate, providing a gap between the board mounting face and the firstsurface of the circuit board substrate. In an exemplary embodiment, anelectrical inter-connection system includes a circuit board substrateand a conductive body. In accordance with this embodiment, the circuitboard substrate includes at least one aperture defined by a sidewallhaving a conductive surface. In addition, the conductive body has atleast one protrusion extending from a base, the protrusion engaging twospaced-apart portions of the sidewall when the protrusion is inserted inthe aperture, and the protrusion being seized within the aperture withan interference fit between the protrusion and the two spaced-apartportions, e.g., the protrusion having a draft angle between 1 and 3degrees. The spaced-apart portions may comprise a flat surface, and theprotrusion may have a generally cylindrical shape. The aperture mayextend between the first and second surfaces and may have an eccentricshape or may be shaped as a slot having a length and a width, e.g., thedifference between said slot width and the protrusion diameter beingbetween 1.5% and 20% of the slot width. Optionally, the conductive padsmay occupy a portion of the periphery of the through-hole or may besubstantially annular in shape, surrounding the through-hole on one ormore sides of the circuit board.

In another illustrative embodiment of the invention, an electricalinter-connection system comprises a pin block that holds at least oneconductive pin. The pin block includes at least one stand-off featurethat provides a gap between a body portion of the pin block and thecircuit board so that solder screened onto one surface of the circuitboard substrate can flow into the plated through-hole during re-flowprocessing. The gap further provides space for a solder fillet to formbetween the conductive pin and a conductive pad during processing. Inyet another exemplary embodiment, an electrical inter-connection systemcomprises a circuit board having an eccentric aperture suitable forconnection with a protruding cylindrical feature on an electricalground, such as a die cast aluminum housing, which may not be suitablefor soldering, i.e., which exhibits poor solderability. In accordancewith this embodiment, the eccentric aperture is plated with a conductivematerial, which is electrically connected with circuitry on the circuitboard. Accordingly, when the circuit board is pressed onto theprotruding cylindrical feature, electrical connection is establishedamong the circuit board and the electrical ground due to theinterference contact between the protrusion and the plated conductivematerial on the aperture, thereby optimizing normal forces acting uponthe grounding inter-connection so as to provide adequately low,electrical contact resistance with reduced net stresses.

In a further aspect, the invention provides an improved method forproducing an electrical inter-connection among a circuit board and oneor more conductive elements located on the major sides of the circuitboard. In accordance with various embodiments, the invention enables aconductive terminal to be inserted into a through-hole in a circuitboard and electrically connected with the circuit board withoutrequiring an interference fit. Accordingly, the invention facilitateslow-cost, high volume production involving filtered electricalconnectors.

In an exemplary embodiment, a circuit board inter-connection methodenables a conductive terminal to be electrically connected with acircuit board having a plated through-hole. In an exemplary embodiment,a conductive pin or terminal suitable for connecting a circuit boardwith conductive elements on each major side of the circuit board isinserted into a through-hole and electrically, and optionally,mechanically connected with the circuit board using a single re-flowprocess. In an exemplary re-flow process, solder paste or anotherconductive bonding agent is applied to one or more side of the circuitboard and processed through a re-flow oven one or more time to establishthe connection among the circuit board and the terminal.

In an exemplary embodiment, a circuit board inter-connection method isprovided for forming an electrical connection in a through-hole definedin a circuit board substrate. In accordance with this embodiment, amethod includes providing a circuit board substrate having first andsecond surfaces and a through-hole extending between the first andsecond surfaces; providing a conductive terminal having first and secondends; providing a first conductive pad on the first surface of thecircuit board substantially adjacent the through-hole; placing aconductive bonding agent on the first conductive pad; placing theterminal into the through-hole such that the first end is exposed forelectrical connection with a mating element on the first side of thecircuit board, and the second end is exposed for electrical connectionwith a mating element on the second side of the circuit board; andre-flowing the conductive bonding agent, causing it to flow into thethrough-hole so that it electrically connects the terminal with thefirst conductive pad.

In another exemplary embodiment, a circuit board inter-connection methodincludes the step of providing a second conductive pad on the secondsurface of the circuit board, substantially adjacent the through-holeand the step of causing the bonding agent to flow includes causing theconductive bonding agent to flow through the through-hole such that theconductive bonding agent electrically connects said terminal with thesecond conductive pad.

In another exemplary embodiment, a circuit board inter-connection methodincludes the step of placing a stencil over the through-hole beforeplacing a conductive bonding agent on the first conductive pad, wherebythe conductive bonding agent is prevented from being placed in thethrough-hole. The method may comprise the step of removing the stencilbefore placing the terminal into the through-hole.

In another exemplary embodiment, a circuit board inter-connection methodincludes providing a pin block, the pin block comprising a dielectrichousing having a body and at least one stand-off, the body having aboard mounting face and an opposed mating face, and the at least onestand-off extending from the board mounting face. The method may alsoinclude the step of positioning the terminal in the pin block such thatthe first end extends through the body between the board mounting faceand the mating face. The step of placing the terminal into thethrough-hole may include placing the at least one stand-off on the firstsurface of the circuit board substrate, and the body may be located asufficient distance from the circuit board to enable a solder fillet toform between the conductive terminal and the first conductive pad.

These and other features and advantages of the present invention willbecome apparent from the following brief description of the drawings,detailed description, and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned objects and features of the present invention can bemore clearly understood from the following detailed descriptionconsidered in conjunction with the following drawings, in which likenumerals represent like elements and in which:

FIG. 1 illustrates a sectional view of an inter-connection system inaccordance with an exemplary embodiment of the present invention;

FIG. 2 illustrates a side view of a pin block and terminal in accordancewith an exemplary embodiment of the present invention;

FIG. 3 illustrates a bottom plan view of a pin block and terminal inaccordance with an exemplary embodiment of the present invention;

FIGS. 4(a)-4(d) illustrate top plan views showing the steps of a methodin accordance with an exemplary embodiment of the present invention;

FIG. 5 illustrates a flow chart of a method in accordance with anexemplary embodiment of the present invention;

FIG. 6 illustrates a top plan view of a second aspect of aninter-connection in accordance with an exemplary embodiment of thepresent invention;

FIG. 7 illustrates a view taken along line 7-7 of FIG. 6; and

FIG. 8 illustrates a view taken along line 8-8 of FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

As discussed above, the methods and systems of the present inventionprovide improved electrical inter-connection among a circuit board andone or more conductive elements located on each major side of thecircuit board, accommodating use of low-cost circuit board substrateswhile providing electrical grounding and significantly reducing oreliminating insertion forces and stresses that might otherwise damagecircuit traces, solder joints, and electronic components.

Referring to the figures, FIG. 1 illustrates an exemplary embodiment ofa first aspect 10 of the electrical inter-connection system of thepresent invention. First aspect 10 includes a circuit board 12 having aplated through-hole 14 extending between first and second surfaces 16,18 of circuit board 12, an annular first conductive pad 20 disposed onfirst surface 16 surrounding and substantially adjacent platedthrough-hole 14, and an annular second conductive pad 22 disposed onsecond surface 18 surrounding and substantially adjacent platedthrough-hole 14. Circuit board 12 is made of a standard FR-4 epoxy-glassmaterial. It should be noted that other circuit board materials such aspolymide-glass, benzocyclobutene, Teflon, other epoxy resins, injectionmolded plastic, ceramic, or the like may also be used as may othersuitable circuit board materials known to those skilled in the art.

A pin block 24 is positioned on first surface 16 of circuit board 12.Conductive pin 26 or terminal is positioned in pin block 24 and extendsthrough plated through-hole 14. Conductive pin 26 has first and secondends 28, 30, each end 28, 30 including a respective exposed protrudingportion 32, 34 for connection with a mating element (not shown), such asa female terminal or a through-hole in a second circuit board. Theexposed protruding portions 32, 34 each extend at least about 2 mmbeyond respective first and second surfaces 16, 18 of circuit board 12and further extend a sufficient distance, as necessary, to mate with aselected mating element. Solder 36 electrically connects the conductivepin 26 with first and second conductive pads 20, 22. It should be notedthat other conductive bonding agents such as conductive epoxy may alsobe used. Pin block 24 includes a body 38 having a board mounting face 40and an opposed mating face 42 and at least one integral stand-offfeature 46 extending from board mounting face 40 that provides a gap 44between body 38 and circuit board 12. Gap 44 between body 38 and circuitboard 12 provides space for solder paste 36 a (as shown on FIGS. 4 b and4 c), which is applied to first surface 16 of circuit board 12 to flowinto plated through-hole 14 during re-flow processing. Gap 44 furtherprovides space for a solder fillet 48 to form between conductive pin 26and first conductive pad 20.

As shown on FIGS. 2 and 3, an exemplary embodiment of pin block 24 ofthe present invention includes a plurality of spaced conductive pins 26.Conductive pins 26 may be held in place by slip fit, one or moreinterference feature formed in the body of the pin, an insert-moldingprocess, or any other suitable mechanism. Pin block 24 is molded of adielectric material, preferably plastic, with a plurality of stand-offfeatures 46, which provide gap 44 between body 38 of pin block 24 andfirst surface 16 of circuit board 12. Stand-off features 46 are locatedbased on desired circuit board 12 geometry and pin 26 arrayconfiguration to minimize contact with first conductive pad 20 and otherareas where solder paste 36 a is screened onto circuit board 12. Asshown on FIG. 1, stand-off feature 46 is designed to minimize surfacearea contact by tapering to a small geometric shape, such as a circle orrectangle from body 38 of pin block 24. This taper also serves to aidmold release when plastic pin block 24 is manufactured. It is importantthat these features, as part of pin block 24, be made of a material thatwill withstand processing temperatures, such as those in a typicalsolder re-flow process.

FIGS. 4(a)-4 (d) and FIG. 5 illustrate an exemplary method 100 ofmanufacture according to the present invention. Referring first to FIG.4(a), the circuit board (as shown on FIG. 1) is provided with platedthrough-hole 14. Annular first conductive pad 20 is disposed on firstsurface 16 (as shown on FIG. 1) surrounding and substantially adjacentplated through-hole 14, and annular second conductive pad 22 is disposedon second surface 18 (as shown on FIG. 1) surrounding and substantiallyadjacent plated through-hole 14.

As shown on FIG. 4(b), a layer of a solder paste 36 a is applied tofirst conductive pad 20 using a screening process. Other conductivebonding agents and application processes known to those skilled in theart may also be used. Pin an exemplary embodiment, a stencil is utilizedduring this step to mask the area over and around plated through-hole 14to keep solder paste 36 a away from plated through-hole 14. Thus, aspace 50 is provided between layer of solder 36 and plated through-hole14, enabling conductive pin 26 to be inserted without contacting solderpaste 36 a. This is important because, if solder paste 36 a adheres toconductive pin 26, it may cause normal forces to increase duringsubsequent mating operations, creating a less aesthetically appealingproduct. In a separate step (not shown), conductive pin 26 is positionedin pin block 24.

As shown on FIG. 4(c), conductive pin 26 is placed in platedthrough-hole 14 such that pin block 24 is seated on first surface ofcircuit board 12 (as shown on FIG. 1) and each of first and second ends28, 30 of conductive pin 26 project beyond respective first and secondsurfaces 16, 18 of circuit board 12 (as shown on FIG. 1). Conductive pin26 is held in place by pin block 24 (as shown on FIG. 1), by a fixture(not shown), or another method within the scope of the presentinvention.

Solder paste 36 a may be re-flowed in a conventional re-flow process,which melts solder paste 36 a. Melted solder 36 is drawn towardconductive pin 26, forming solder fillet 48 between conductive pin 26and first conductive pad 20. FIG. 4(d) and FIG. 1 illustrate conductivepin 26, solder 36, and first conductive pad 20 after solder paste 36 ahas been re-flowed.

Referring now to FIG. 5, an exemplary method 100 includes the steps of:

providing a circuit board substrate with a through-hole extendingbetween first and second surfaces 102, wherein through-hole includesconductive plating extending between first and second surfaces;

providing a first conductive pad on the first surface of circuit boardsubstrate substantially adjacent through-hole 104;

providing a second conductive pad on second surface of circuit boardsubstrate substantially adjacent plated through-hole (not shown on FIG.5);

providing a stencil on first surface of circuit board to maskthrough-hole and a small annular area immediately surroundingthrough-hole (not shown on FIG. 5);

applying sufficient solder paste to first conductive pad to form arobust solder joint 106, preferably utilizing stencil or anothermechanism to prevent solder paste from being placed in through-hole;

removing stencil (not shown on FIG. 5);

providing a conductive pin or terminal having first and second ends 108;

providing a pin block having a dielectric housing including a body andat least one stand-off, the body having a board mounting face and anopposed mating face, the at least one stand-off being capable ofproviding a gap for solder to flow and for a solder fillet to formbetween the conductive pin and the first conductive pad when the pinblock is connected with the circuit board (not shown on FIG. 5);

positioning the conductive pin in the pin block such that first endextends through body between board mounting face and mating face (notshown on FIG. 5);

placing the conductive pin in through-hole such that each of first andsecond ends project beyond respective first and second surfaces ofcircuit board substrate 110, when pin block is utilized, this stepfurther includes placing at least one stand-off on first surface ofcircuit board substrate, thereby leaving sufficient gap between body ofpin block and first surface of circuit board for solder to flow and forsolder fillet to form between conductive pin and first conductive pad;and

re-flowing solder paste by heating or other methods known to thoseskilled in the art so that solder paste melts and flows intothrough-hole, forming solder joint between first conductive pad andconductive pin 112 and, optionally, between second conductive pad andconductive pin when second conductive pad is provided on second surfaceof circuit board.

This method is particularly advantageous when the opposing side of thecircuit board is densely populated with components, thereby leavinglittle or no room to apply the conductive bonding agent to the opposingside. As discussed above, in an exemplary embodiment of the method, astencil is placed over and around plated through-hole before conductivebonding agent is applied to circuit board to keep conductive bondingagent away from plated through-hole. This enables the terminal to beinserted into the plated through-hole without contacting conductivebonding agent, which, if it adheres to terminal, causes normal forces toincrease during subsequent mating operations and creates anaesthetically unappealing product. Importantly, the invention enables anelectrical and mechanical connection to be established without the needfor an interference fit, which might otherwise causes stresses, fatigue,and/or damage to circuit traces, solder joints, and electroniccomponents.

The embodiment of the method as shown on FIGS. 4(a)-4(d) and FIG. 5 andas described above is provided merely by way of example and is notintended to limit the scope of the invention in any way. All steps arenot required in all applications. Other modifications may occur to oneskilled in the art. For example, solder may be replaced by otherconductive bonding agents known to those skilled in the art.Furthermore, it is not necessary to use a pin block in all applications.Nor is it necessary that the through-hole be plated or that the secondconductive pad be placed on the second side of the circuit board,particularly when it is not necessary to provide electrical connectionwith circuitry on the second side of the circuit board. Nor is itnecessary that a stencil be used during the step of applying the solderpaste.

FIGS. 6-8 illustrate a second aspect 200 of the present invention. In anexemplary embodiment, second aspect 200 is suitable for providing aninterference fit electrical connection among a circuit board and aground having poor solderability characteristics. This embodimentoptimizes normal forces, for lower stresses, yet enables adequately lowelectrical contact resistance, such as 10 milliohms, or less in oneembodiment.

In the second aspect 200, the circuit board 12 has an eccentric aperture202 defined by a sidewall 204. Aperture 202 has a narrow portion 206 anda wide portion 208. Sidewall 204 has a conductive plating 210, forexample, tin/lead over copper, which is connected with circuitry oncircuit board 12. Second aspect 200 further includes a protrudingcylindrical feature 212 extending from a base 214 on an electricalground 216. It should be noted that ground 216 may have poorsolderability characteristics, such as when a die cast aluminum housingis used as a ground. Circuit board 12 is pressed onto protrudingcylindrical feature 212, such that protruding cylindrical feature 212extends into eccentric aperture 202, establishing an electricalconnection among circuit board 12 and electrical ground 216 due to theinterference contact between protruding cylindrical feature 212 andplated conductive material 210 in aperture 202.

In an exemplary embodiment, cylindrical feature 212 has a 1 to 3 degreedraft angle 218, and the difference between diameter 220 of cylindricalfeature 212 as measured at base 214 and aperture 202 width at narrowportion 206 is about 1.5% to 20% of aperture 202 width. Thisconfiguration enables circuit board 12 to seize protruding cylindricalfeature 212 at two spaced-apart opposing portions 222, 224 of sidewall204 upon inserting protruding cylindrical feature 212 into aperture 202,and once inserted, protruding cylindrical feature 212 is seized withinaperture 202 at solely opposing portions 222, 224 with an interferencefit between protruding cylindrical feature 212 and opposing portions222, 224. Further, the length as measured at wide portion 208 isgenerally at least 34% larger than the width as measured at narrowportion 206 to prevent circuit board 12 from seizing protrudingcylindrical feature 212 at more than two points.

The preferred embodiments shown and described herein are provided merelyby way of example and are not intended to limit the scope of theinvention in any way. Preferred dimensions, ratios, materials andconstruction techniques are illustrative only and are not necessarilyrequired to practice the invention. It is intended that the scope of thepresent invention herein disclosed should not be limited by theparticular disclosed embodiments herein, but should be defined only by afair reading of the claims that follow.

Further modifications and alterations may occur to others upon readingand understanding the specification. For example, the circuit board 12may include a plurality of spaced eccentric apertures 202 to mate with abody, such as ground 216, having a plurality of correspondingprotrusions 212 to provide a mechanical and/or electrical connection. Itis intended to include all such modifications and alterations insofar asthey come within the scope of the invention.

1-11. (canceled)
 12. An electrical inter-connection system comprising: acircuit board substrate including at least one aperture, said aperturebeing defined by a sidewall having a conductive surface; and aconductive body having at least one protrusion extending from a base,said protrusion engaging two spaced-apart portions of said sidewall uponinserting said protrusion in said aperture, and once inserted, saidprotrusion being seized within said aperture at said two spaced-apartportions with an interference fit between said protrusion and said twospaced-apart portions.
 13. An electrical inter-connection system asrecited in claim 12, wherein said aperture has an eccentric shape. 14.An electrical inter-connection system as recited in claim 13, whereineach of said two spaced-apart portions comprise a flat surface.
 15. Anelectrical inter-connection system as recited in claim 14, wherein saidprotrusion has a generally cylindrical shape,
 16. An electricalinter-connection system as recited in claim 15, wherein said circuitboard substrate has a first surface and opposing second surface, saidaperture extending between said first and second surfaces.
 17. Anelectrical inter-connection system as recited in claim 16, wherein saidaperture is shaped as a slot having a length and a width.
 18. Anelectrical inter-connection system as recited in claim 17, wherein thedifference between said slot width and said protrusion diameter isbetween 1.5% and 20% of said slot width.
 19. An electricalinter-connection system as recited in claim 12, wherein said protrusionhas a draft angle between 1 and 3 degrees.